Hedge-fund managers and other large speculators this month boosted bets to the most since January that the securities will fall. That was just in time for the Federal Reserve to trigger the biggest rally in short-term debt since 2009 on Wednesday when it reduced estimates for borrowing costs.

It’s a third time unlucky for bearish investors after they increased net short positions to a 4 1/2-year high before Treasuries surged in January. They then reduced those wagers by more than 80 percent ahead of the worst month in almost two years.

“The pricing was always that we’ll see the Fed become slightly more hawkish and reiterate liftoff around the middle of next year,” said Stan Shamu, a markets strategist at IG Ltd. in Melbourne. “There’s a lot of short covering. It’s quite clear that more people were on the other side of the trade.”

The U.S. two-year yield dropped 12 basis points, or 0.12 percentage point, on Wednesday to 0.56 percent, the biggest decline since March 2009, according to Bloomberg Bond Trader data.

The rate rose two basis points Thursday to 0.58 percent as of 7:50 a.m. New York time. The 0.5 percent note due in February 2017 fell 2/32, or 63 cents per $1,000-face amount, to 99 27/32. The benchmark 10-year yield increased two basis points to 1.94 percent, having dropped 13 basis points Wednesday.

Treasuries lost 1.7 percent in February, the biggest monthly decline since May 2013, after returning 2.9 percent in January, the best month since December 2008, according to Bank of America Merrill Lynch indexes.

Short Positions

Net short positions — bets against 10-year Treasuries — rose to 139,474 contracts in the week through March 3, according to data from the U.S. Commodity Futures Trading Commission. They fell as low as 44,816 contracts in February, from 261,282 contracts as of Dec. 30, which was the most since May 2010.

The Fed said Wednesday it will need to see more progress in the jobs market and gain confidence that inflation is accelerating, even as it dropped its pledge to be “patient” in its approach to a less-stimulative monetary policy.

Fed officials lowered their median estimate for the federal funds rate at the end of 2015 to 0.625 percent, compared with 1.125 percent in December forecasts.

The Fed’s median estimate for the end of 2016 declined to 1.875 percent from 2.5 percent, according to the Federal Open Market Committee’s quarterly Summary of Economic Projections.

“It’s clearly a dovish surprise from the Federal Reserve,” said Tony Morriss, interest-rate strategist for Australia and New Zealand at Bank of America Merrill Lynch in Sydney. “A key message from the forecasts was that any rise in U.S. rates is going to be quite gradual.”

The likelihood U.S. policy makers will boost their benchmark rate from near zero by September fell to 40 percent from 55 percent on Tuesday, according to calculations by Bloomberg using federal fund futures contracts. Futures traders have all but wiped out the chance of an increase in June, assigning it a 11 percent probability.

Treasury bears just can't catch a break.Hedge-fund managers and other large speculators this month boosted bets to the most since January that the securities will fall. That was just in time for the Federal Reserve to trigger the biggest rally in short-term debt since 2009...